[StirCrazy]

Originally Posted by sphelps

It's actually slightly more complicated if you really want to get into it. The structure supporting the floor has a minimum requirement for weight but it's based on the actual room size and it's 40lbs/sqft.

It works like this, if the room is say 20 feet by 15 feet that's 300 sqft. Multiply that by 40lbs/sqft and you get the minimum load rating for the room which in this case would be 12000lbs. So that means the floor structure must support 12000lbs total room weight and as far I as I know that's only dead weight so there is additional safety for live weight. This is also a minimum and most house exceed this rating.

When it comes to adding concentrated weight like from say a fish tank you still need to think it through a little as the above formula certainly doesn't mean you can stick all that weight in one spot. However in your case it's not an overly large tank and it's very long so the weight will be distributed quite well.

Now your tile may have a max psi rating but it will be far beyond what your tank will do. You can drive a car on most tile.

all good points but missing one important thing. deflection. floors for tile have to be braced up (by various methods) to decrease the amount of deflection. this is one of the biggest shortcuts builders take, by not doing the required work to stiffen the flor system to lower the amount of deflection in the floor. the result of this is most comenly cracked grout lines and tiles. by putting a larger then normal load in one area you are creating a situation where deflection is increased. to me this is more of a concern than the actualy weight of the tank. if you had carpet floors you would be fine as is I would guess as Sphelps has hinted at, but my concern is the extra deflection the tank weight would cause.

another idea (not sure if it is feasable or not,) would be to run two 2X10, parallel to the foundation wall at equal distances between them. then put two beams to suport them. this would not rely on a slab point load but would drop your celing hight 20" in that area. if you are putting a tank in that area it might not be a concern as you could make the tank a built in and it would just be your fish room that has a lowered celing high if I am understanding the size right.

there are probably 10 ways to skin this cat, best bet would be to find a local person, who even if you have to pay 100.00 bucks. to give you there opinion. maybe talk to a couple good builders and ask them what they think you would have to do, make sure you bring up the tiled floor and deflection concerns.

Steve